Oxidation Resistance

MULTIMET® exhibits acceptable oxidation resistance up to around 1800°F. However, due to concerns with oxidation resistance, MULTIMET® has been generally replaced by 556® alloy, which has comparable creep-rupture strength but superior oxidation resistance, particularly at temperatures greater than 1800°F.

Short-term Oxidation

Comparative Oxidation Resistance in Flowing Air, 1008 Hours

Alloy

1800°F (980°C)

2000°F (1095°C)

Metal Loss

Average Metal Affected

Metal Loss

Average Metal Affected

mils

μm

mils

μm

mils

μm

mils

μm

MULTIMET®

0.4

10

1.3

33

8.9

226

14.3

363

556®

0.4

10

2.3

58

1.5

38

6.9

175

Flowing air at a velocity of 7.0 ft/min (213.4 cm/min) past the samples. Samples cycled to room temperature once per week.

Dynamic Oxidation Burner Rig

Alloy

1600°F (870°C), 1000 h, 30-min cycles

1600°F (870°C), 2000 h, 30-min cycles

Metal Loss

Average Metal Affected

Metal Loss

Average Metal Affected

mils

μm

mils

μm

mils

μm

mils

μm

MULTIMET®

1.3

33

2.2

56

2.7

69

4.9

124

556®

1.4

36

3.1

79

1.5

38

3.9

99

Burner rig oxidation tests were conducted by exposing sampIes 3/8 in. x 2.5 in. x thickness (9 mm x 64 mm x thickness), in a rotating holder, to products of combustion of No. 2 fuel oil burned at a ratio of air to fuel of about 50:1. (Gas velocity was about 0.3 mach). Samples were automatically removed from the gas stream every 30 minutes and fan-cooled to near ambient temperature and then reinserted into the flame tunnel.